Air force Radar Academy
Air force Radar Academy
News Article | August 1, 2017
The U.S. Energy Information Administration has released its 2017 World Oil Transit Chokepoints report. Chokepoints are narrow channels along widely used global sea routes for oil transport, with some so narrow that restrictions are placed on the size of the vessel that can navigate through them. The inability of oil tankers to transit a major chokepoint, even temporarily, can lead to substantial supply delays and higher shipping costs, resulting in higher world energy prices. While most chokepoints can be circumvented by using other routes that add significantly to transit time, no practical alternatives are available in some cases. Chokepoints may also expose oil tankers to theft from pirates, terrorist attacks, political unrest, and shipping accidents. By volume of oil transit, the Strait of Hormuz (leading out of the Persian Gulf) and the Strait of Malacca (linking the Indian and Pacific Oceans) are the world’s most important strategic chokepoints. The Cape of Good Hope, near the southern tip of Africa, is a major oil trade route and potential alternate route to certain chokepoints. Ships carrying crude oil and petroleum products transiting certain chokepoints are in some cases limited by size restrictions. The global crude oil and refined product tanker fleet is typically classified using the Average Freight Rate Assessment (AFRA) system that was first established by Royal Dutch Shell many years ago and is now overseen by an independent group of shipping brokers. The AFRA system classifies tanker vessels according to deadweight tons—a measure of a ship’s capacity to carry cargo. The approximate capacity of a ship in barrels is determined using an estimated 90% of a ship’s deadweight tonnage, which is multiplied by a barrel-per-metric-ton conversion factor specific to each type of petroleum product and crude oil, because liquid fuel densities vary by type and grade. Long Range (LR) class ships are the most common ships in the global tanker fleet, as they are used to carry both refined petroleum products and crude oil. These ships can access most large ports that ship crude oil and petroleum products. An LR1 tanker can carry between 345,000 barrels and 615,000 barrels of gasoline (14.5–25.8 million gallons) or between 310,000 barrels and 550,000 barrels of light sweet crude oil. An LR2 tankers can carry 600,000 to 900,000 barrels of a petroleum product like gasoline, diesel, or light sweet crude oil. Additional ship categories, including the Very Large Crude Carrier (VLCC) and the Ultra-Large Crude Carrier (ULCC), were added to the AFRA classification system as larger vessels with better economics for crude oil shipments were deployed to serve expanded global oil trade. VLCCs are responsible for most crude oil shipments around the globe and can carry between 1.9 million and 2.2 million barrels of a West Texas Intermediate-type crude oil. Some chokepoints, such as the Strait of Hormuz, are sufficiently deep and wide to accommodate all sizes of vessels. However, ships transiting the Panama and Suez canals are subject to depth and width restrictions. Tanker traffic through the Bab el-Mandeb and Turkish straits do not face specific size restrictions, but they must deal with relatively narrow, difficult-to-navigate sea lanes. More information about energy product flows through these points is available in EIA’s 2017 World Oil Transit Chokepoints analysis.
Liang J.,Huizhou University |
Xu B.,North China University of Water Conservancy and Electric Power |
Cai Z.,Air force Radar Academy
Journal of the Optical Society of America B: Optical Physics | Year: 2011
Internal modes and internal oscillation of necklace solitons in Bessel photonic lattices imprinted in selfdefocusing and self-focusing materials are investigated. Under the same parameters, necklace solitons in selffocusing material possess larger power than that of self-defocusing material, and the stability of solitons in defocusing material is better than in focusing material. It is shown that the internal modes have both real and imaginary parts in such cases, differing from the one-dimensional case. While white noise gives rise to jitter of the intensity of stable necklace solitons, the stable solitons perform long-distance and quasi-periodic oscillation of intensity and shape under the perturbation of internal modes, and the solitons in self-defocusing material experience larger oscillation amplitude than that in self-focusing material. © 2010 Optical Society of America.
Xu J.,Air force Radar Academy |
Yu J.,Tsinghua University |
Peng Y.-N.,Tsinghua University |
Xia X.-G.,University of Delaware
IEEE Transactions on Aerospace and Electronic Systems | Year: 2011
Based on the coupling relationship among radial velocity, range walk, and Doppler frequency of the moving target's echoes, a novel method is proposed, i.e., Radon-Fourier transform (RFT), to realize the long-time coherent integration for radar target detection. The RFT realizes the echoes spatial-temporal decoupling via joint searching along range and velocity directions, as well as the successive coherent integration via the Doppler filter bank. Besides, four equivalent RFTs are obtained with respect to the different searching parameters. Furthermore, a generalized form of RFT, i.e., generalized Radon-Fourier transform (GRFT), is also defined for target detection with arbitrary parameterized motion. Due to the similarity between the RFT and the well-known moving target detection (MTD) method, this paper provides detailed comparisons between them on five aspects, i.e., coherent integration time, filter bank structure, blind speed response, detection performance, and computational complexity. It is shown that MTD is actually a special case of RFT and RFT is a kind of generalized Doppler filter bank processing for targets with across range unit (ARU) range walk. Finally, numerical experiments are provided to demonstrate the equivalence among four kinds of RFTs. Also, it is shown that the RFT may obtain the coherent integration gain in the different noisy background and the target's blind speed effect may be effectively suppressed. In the meantime, both the weak target detection performance and the radar coverage of high-speed targets may be significantly improved via RFT without change of the radar hardware system. © 2006 IEEE.
Nie T.,Air force Radar Academy |
Sheng W.,Air force Radar Academy
Xi Tong Gong Cheng Yu Dian Zi Ji Shu/Systems Engineering and Electronics | Year: 2010
Supply support optimizing is an important approach to improve operational readiness and reduce life cycle cost for equipments. Through analyzing the two-echelon supply support system for repairable spare parts of complex equipment, and researching the relationship of spare parts support and operational readiness, a supply support optimizing model is proposed, which chooses system supply availability as the object and the total acquisition cost as the subject. Marginal efficiency analysis algorithm is applied to achieve the optimization. Finally, several examples are given to verify that this model can optimize spare parts storage, and evaluate the effects on support efficiency of some important factors, including different stock, repair capacity of two levels, reliability and so on.
Chen Y.,Air force Radar Academy |
Xia M.,Air force Radar Academy |
Zhu Z.,Air force Radar Academy
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012
Aiming at the problems of traditional photovoltaic grid-connected system structure, a new type of photovoltaic grid-connected cascaded inverter scheme with stepped waveforms and instantaneous value feedback hybrid control. In this method, one part of the cascaded units use stepped waveforms control, the other part use octave sinusoidal pulse width modulation (SPWM) control with instantaneous current feedback. The output voltage comes from the two parts in series. The analysis of the output voltage harmonic shows that the amplitude of the output voltage and the power factor can be adjusted by the SPWM wave phase-shift angles; the low order harmonic of the output voltage is aroused by the stepped waveforms control part, which is the theoretic background for the output filter design. A simple algorithm for the trigger angles of the stepped waveforms modulated inverter is proposed, which is not only fit for the cascaded inverter with different voltage steps, but also fit for online calculation. The experimental results show that this scheme has simple structure, high reliability and low switching loss.
Ren J.,Air force Radar Academy
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011
To further research the multifractality of sea clutter, multifractality of IPIX radar sea clutter has been analyzed by Qth-order Moment Structure Partiction Function (Q-MSPF) method in detail in this paper, through simulation analysis, two target detection methods based on analysis of the mass exponent function and the source of multifractality are proposed, and proved to be effective. © 2011 IEEE.
Xiao L.,Air force Radar Academy |
Guo L.,Air force Radar Academy
CCTAE 2010 - 2010 International Conference on Computer and Communication Technologies in Agriculture Engineering | Year: 2010
Based on the analysis of the development of agricultural mechanization, the trend of agricultural service system reform, agricultural environment protection and the development of information technology, it is possible to realize the precision agriculture. This paper designs the agricultural environmental monitoring system based on the wireless sensor network (WSN). The system can real-timely monitor agriculture environmental information, such as the temperature, humidity, and light intensity. This paper introduces the theory of the monitoring system, and discusses the aspect of hardware and software design of the composed modules, network topology, network communication protocol and the present challenges. Experiments show that the node can achieve agricultural environmental information collection and transmission. The system has the feature of compact in frame, light in weight, steady in performance and facilitated in operation. It greatly improves the agricultural production efficiency and automatic level drastically. © 2010 IEEE.
Liu J.,Huazhong University of Science and Technology |
Liu J.,Mechanical Engineering Institute |
Wu C.,Air force Radar Academy |
Liu W.,Huazhong University of Science and Technology
Decision Support Systems | Year: 2013
Recommendation systems have received great attention for their commercial value in today's online business world. However, most recommendation systems encounter the data sparsity problem and the cold-start problem. To improve recommendation accuracy in this circumstance, additional sources of information about the users and items should be incorporated in recommendation systems. In this paper, we modify the model in Bayesian Probabilistic Matrix Factorization, and propose two recommendation approaches fusing social relations and item contents with user ratings in a novel way. The proposed approach is computationally efficient and can be applied to trust-aware or content-aware recommendation systems with very large dataset. Experimental results on three real world datasets show that our method gets more accurate recommendation results with faster converging speed than other matrix factorization based methods. We also verify our method in cold-start settings, and our method gets more accurate recommendation results than the compared approaches. © 2013 Elsevier B.V.
Ma N.,Air force Radar Academy
Huazhong Keji Daxue Xuebao (Ziran Kexue Ban)/Journal of Huazhong University of Science and Technology (Natural Science Edition) | Year: 2010
The system could not give full play to its performances, because multiple network cards and multiple connections technology in iSCSI can not appropriately assign every task of the system. Thus, a dynamic load balancing algorithm using a feedback control mechanism is proposed to improve the whole performance in iSCSI system. This algorithm adopts a feedback technology, collects much resource states in the whole system, and calculates the real-time feedback's value, combines the previous feedback's value to assign every system's task in order to dynamically adjust the system's load state. The test results show that the performance is improved with this algorithm.
Sheng W.,Air force Radar Academy |
Ren J.,Air force Radar Academy
Dianbo Kexue Xuebao/Chinese Journal of Radio Science | Year: 2011
Multifractal theory is introduced for modeling HF radar sea clutter, and a new time-domain model based on multifractal for HF sea clutter is presented. Simulation analysis indicates that the multifractal model has a similar multifractality with real sea clutter data by comparison among multifractal model, real sea clutter data and Fractional Brownian Motion(FBM) model. In addition, by using probability density function comparison analysis among 3 most commonly used distributions such as Weibull, Log-Normal and Rayleigh distribution, and through a statistical test by modified Kolmogorov- Smirnov(K-S), the conclusion of the proposed multifractal model of HF radar sea clutter possesses the apriori statistical characteristics is obtained, which further proves that this time-domain multifractal model for HF radar sea clutter is quite reasonable and effective. © 2011 by Editorial Department of Chinese Journal of Radio Science.